In $p\overline{p}$ collisions at $\sqrt{s}=1.8$ TeV we find jet events with a rapidity gap topology. The number of hadrons in the rapidity interval $\ensuremath{\Delta}{\ensuremath{\eta}}_{D}$ between leading-jet cones was sampled by charged tracks with ${P}_{T}>400$ MeV/c. We find excess trackless events beyond that expected in a smooth multiplicity distribution. In a control region outside $\ensuremath{\Delta}{\ensuremath{\eta}}_{D}$ we see no excess. For $\ensuremath{\Delta}{\ensuremath{\eta}}_{D}>0.8$, the fraction of excess trackless events, consistent with estimates based on exchange of color-singlet digluons, is $R(\mathrm{gap})=\frac{{\ensuremath{\sigma}}_{\mathrm{jet}}(\mathrm{gap})}{{\ensuremath{\sigma}}_{\mathrm{jet}}}=0.0085\ifmmode\pm\else\textpm\fi{}{0.0012(\mathrm{stat})}_{\ensuremath{-}0.0012}^{+0.0024}(\mathrm{syst})$.

We measure the Drell-Yan differential cross section d2sigma/dM dy\Absolute value of y < 1 over the mass range 11 < M < 150 GeV/C2 using dielectron and dimuon data from ppBAR collisions at a center-of-mass energy of square-root s = 1.8 TeV. Our results show the 1/M3 dependence that is expected from the naive Drell-Yan model. In comparison to the predictions of recent QCD calculations we find our data favor those parton distribution functions with the largest quark contributions in the x interval 0.006 to 0.03.

This paper reports the measurement of the B meson and b quark cross sections through the decay chain B0 --> J/psi K* (892)0, J/psi --> mu+ mu-, K* (892)0 --> K+ pi-, using 4.3 pb-1 of data collected at the Collider Detector at Fermilab in pBARp collisions at square-root s = 1.8 TeV. We obtain sigma(B) = 1.5 +/- 0.7(stat)+/-0.6(syst) mub for B0 mesons with transverse momentum P(T) > 9.0 GeV/c and rapidity \y\ < 1.0. Using this results, we find sigma(b) = 3.7 +/- 1.6(stat)+/-1.5(syst) mub for b quarks with P(T) > 11.5 GeV/c and rapidity \y\ < 1.0. The b quark cross section is compared to next-to-leading order QCD calculations and previous measurements.

We measure the Drell-Yan differential cross section $\frac{{d}^{2}\ensuremath{\sigma}}{\mathrm{dM}}{dy|}_{|y|<1}$ over the mass range $11<M<150$ GeV/${\mathit{c}}^{2}$ using dielectron and dimuon data from $\overline{p}p$ collisions at a center-of-mass energy of $\sqrt{s}=1.8$ TeV. Our results show the $\frac{1}{{M}^{3}}$ dependence that is expected from the naive Drell-Yan model. In comparison to the predictions of recent QCD calculations we find our data favor those parton distribution functions with the largest quark contributions in the $x$ interval 0.006 to 0.03.

We report a measurement of the diffraction dissociation differential cross section ${\mathit{d}}^{2}$${\mathrm{\ensuremath{\sigma}}}_{\mathrm{SD}}$/${\mathit{dM}}^{2}$dt for p\ifmmode\bar\else\textasciimacron\fi{}p\ensuremath{\rightarrow}p\ifmmode\bar\else\textasciimacron\fi{}X at \ensuremath{\surd}s =546 and 1800 GeV, ${\mathit{M}}^{2}$/s0.2 and 0\ensuremath{\le}-t\ensuremath{\le}0.4 ${\mathrm{GeV}}^{2}$. Our results are compared to theoretical predictions and to extrapolations from experimental results at lower energies.

We present results of a search for a first-generation leptoquark [ital scrS][sub 1] in [ital [bar p]p] collisions at [radical][ital s] =1.8 TeV at the Fermilab Tevatron. Using 4.05 pb[sup [minus]1] of data collected during the 1988--1989 CDF run, we have searched for evidence of [ital scrS][sub 1][ital scr[bar S]1] production assuming that each leptoquark decays to an electron+quark pair with a branching ratio [beta]. Three events with two high energy electrons and two high energy jets were found, but are consistent with [ital Z][sup 0] decay. No events were found in the signal region. Assuming a short lived scalar leptoquark with Yukawa coupling strength [lambda][approx gt]2[times]10[sup [minus]7], we exclude [sigma][beta][sup 2][gt]55(4.0) pb at 95% C.L. for [ital M][sub [ital s][ital c][ital r][ital S]]=45(125) GeV/[ital c][sup 2]. Using a Monte Carlo prediction for [sigma]([ital [bar p]p][r arrow][ital scrS][sub 1][ital scr[bar S]1]+[ital X]), we exclude [ital M][sub [ital s][ital c][ital r][ital S]][lt]113(80) GeV/[ital c][sup 2] for [beta]=100(50)%.

We present a measurement of jet shapes in p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab (CDF). Qualitative agreement is seen with the predictions of recent next-to-leading [O(${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}^{3}$)] calculations and with leading logarithm QCD based Monte Carlo simulations. The dependence of the jet shape on transverse energy is studied.

The dijet invariant mass distribution has been measured in the region between 120 and 1000 GeV/[ital c][sup 2], in 1.8-TeV [ital p[bar p]] collisions. The data sample was collected with the Collider Detector at Fermilab (CDF). Data are compared to leading order (LO) and next-to-leading order (NLO) QCD calculations using two different clustering cone radii [ital R] in the jet definition. A quantitative test shows good agreement of data with the LO and NLO QCD predictions for a cone of [ital R]=1. The test using a cone of [ital R]=0.7 shows less agreement. The NLO calculation shows an improvement compared to LO in reproducing the shape of the spectrum for both radii, and approximately predicts the cone size dependence of the cross section.

We report the full reconstruction of ${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$ mesons through the decay chain ${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$\ensuremath{\rightarrow}J/\ensuremath{\psi} \ensuremath{\gamma}, J/\ensuremath{\psi}\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$, using data obtained at the Collider Detector at Fermilab in 2.6\ifmmode\pm\else\textpm\fi{}0.2 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ of p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s =1.8 TeV. This exclusive ${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$ sample is used to measure the ${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$-meson production cross section times branching fractions. We obtain \ensuremath{\sigma}\ifmmode\times\else\texttimes\fi{}B=3.2\ifmmode\pm\else\textpm\fi{}0.4(stat${)}_{\mathrm{\ensuremath{-}}1.1}^{+1.2}$(syst) nb for ${\mathrm{\ensuremath{\chi}}}_{\mathit{c}}$ mesons decaying to J/\ensuremath{\psi} with ${\mathit{p}}_{\mathit{T}}$>6.0 GeV/c and pseudorapidity \ensuremath{\Vert}\ensuremath{\eta}\ensuremath{\Vert}0.5. From this and the inclusive J/\ensuremath{\psi} cross section we calculate the inclusive b-quark cross section to be 12.0\ifmmode\pm\else\textpm\fi{}4.5 \ensuremath{\mu}b for ${\mathit{p}}_{\mathit{T}}^{\mathit{b}}$>8.5 GeV/c and \ensuremath{\Vert}${\mathit{y}}^{\mathit{b}}$\ensuremath{\Vert}1.

The first prompt photon measurement from the CDF experiment at the Fermilab $p\overline{p}$ Collider is presented. Two independent methods are used to measure the cross section: one for high transverse momentum (${P}_{T}$) and one for lower ${P}_{T}$. Comparisons to various theoretical calculations are shown. The cross section agrees qualitatively with QCD calculations but has a steeper slope at low ${P}_{T}$.

The W production cross section times the branching ratio for W\ensuremath{\rightarrow}l\ensuremath{\nu}, l=e,\ensuremath{\mu} decays has been measured as a function of the associated jet multiplicity. The data have been recorded at the Collider Detector at Fermilab during the 1988--89 run. A recent leading order QCD calculation agrees well with the data up to a jet multiplicity of 4.

We have searched for the b-flavored baryon decay Λb→JψΛ0 in p¯p collisions at √s=1.8 TeV with the Collider Detector at Fermilab (CDF). In the JψΛ0 invariant-mass distribution we observe a flat distribution and a small number of events, consistent with no signal. Using the b-quark cross section measured by the CDF we put an upper limit on the b→Λb production fraction times the branching ratio F(Λb)B(Λb→JψΛ0) of 0.50×10−3 at 90% confidence level.Received 28 September 1992DOI:https://doi.org/10.1103/PhysRevD.47.R2639©1993 American Physical Society